- #1
victorializ
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Homework Statement
Point charges, Q1 = +56 nC and Q2 = -98 nC, are placed as shown. In Figure 18.1a, an external force transports an electron from point A to point B. The work done by the external force is closest to:
A) +620 eV
B) -920 eV
C) -620 eV
D) +920 eV
E) +770 eV
Homework Equations
v= kq/r
W= e (Vb-Va)
The Attempt at a Solution
i know I'm doing this completely wrong. i tried to get the electric potential at A from charge 1 & 2 and then added them. i did the same for the electric potential at point b from charge 1 & 2 . once i had the summed potentials i found the difference and then multiplied by the charge of an electron .
for A[(9 x 10^9) x (56 x 10^-9)/.6] + [(9x 10^ 9) x (-98 x 10^-9)/1 ] = -42 V
for B : [(9 x 10^9) x (56 x 10^-9)/1] + [(9x 10^ 9) x (-98 x 10^-9)/.6] =-966
Vb-Va = -924 V
-924 x (1.6 x 10 ^-19 ) = -1.47 x 10 ^ -16 eV which is nowhere close. i must be approaching this the wrong way.
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